Effects of soil erosion on water quality and water uses in the upper Phong watershed.

The main objective of this paper is to simulate the effects of soil erosion on river water quality and on agricultural production as a result of the transformation of forestlands in the catchment of the upstream Phong River. Suspended solids carry down attached nutrients and agricultural chemicals causing water pollution in the downstream. There are four different types of land use in this simulation, namely forestlands, flatland and highland sugarcane plantation areas, and paddy fields. The highest mean annual amount of soil erosion is from paddy fields (585,700 tons/year), followed by highland (73,800 tons/year) and flatland (63,950 tons/year) sugarcane plantation areas and forestlands (41,800 tons/year), respectively. However, as most of paddy fields are located in a low land and are wet type cultivations, the soil erosion occurred has less impact on river water quality and its production compared to the soil erosion from the steeper slopes of highland plantation areas. Under the resource-based agriculture, the sugarcane production is mainly increased by expanding the plantation areas leading to a significant loss of topsoil and a considerable reduction of agricultural production. Soil erosion contributes to an increase in the average annual suspended solids concentration by 72 mg/l.     

Surface segregation of siloxane containing component in polysiloxane‐block‐polyimide and s‐BPDA/ODA polyimide blends

Surface segregation in polymer blend systems between 3,3′,4,4′‐biphenyltetracarboxylic dianhydride/4,4′‐diaminodiphenyl ether (s‐BPDA/ODA) polyimide and block copolymer based on polysiloxane‐block‐polyimide (SPI) has been investigated. These polyimide blends, having various compositions of the SPI, were processed by a solution casting method. The glass substrate used in the film‐casting process shows significant effect on the migration of surface segregated species to enrich the air‐exposed surface, whereas the more polar s‐BPDA/ODA tends to remain close to the polar glass substrate. X‐ray photoelectron spectroscopy reveals that even at low SPI concentration, the siloxane moieties in the block copolymer tend to segregate into the air side surface. Contact angle measurement evidently indicates an enrichment of the hydrophobic siloxane fraction on the blend film surface. The average water contact angle of glass side surface is 77°C whereas that of the air side is about 102°C in every blend ratio. This behavior confirms the surface segregation phase separation in these polymer blends. Finally, the surface morphology observed by atomic force microscopy also suggests segregation type of phase separation in these blend systems. POLYM. ENG. SCI., 47:489–498, 2007. © 2007 Society of Plastics Engineers.     

Effects of handicraft sitting postures on lower trunk muscle fatigue

Fifteen male subjects were exposed to a primary tracking task and a variety of subsidiary tasks for a total of 15 hours. Tracking performance was assessed through the use of two error measures, amount of time off the target track, and number of times off target. Subsidiary performance tasks included: a vigilance task requiring subjects to respond to the deflection of the noodle of a small meter; two reaction time tasks requiring response to the onset of one or the other of two lights; mental multiplication, which required the solution of simple multiplication problems; and digit span, in which the subject was required to repeat as rapidly and as accurately as possible a sot of digits of either five, six or seven numbers in length. In addition, three physiological measures were obtained.

A significant decrement in trucking performance was obtained for both measures utilized. This decrement was not particularly abrupt in its occurrence but rather took place cumulatively over the entire course of the experiment. There was no clearly established performance decrement on the subsidiary tasks utilized in this investigation. A marked variability in performance over the course of the experimental session was characteristic of performance on these tasks. Performance on the vigilance task, and one of the reaction time tasks improved during the 15-hour test session.

The 17-Kotosteroid and 17-Hydroxyeortieoid values increased during the session but only in the case of the latter was the increase significant. The eosinophil count of subjects exposed to the test conditions decreased steadily throughout the experimental session. However, eosinophil measures obtained from control subjects increased during a similar time period.     

Controlled DNA interpolyelectrolyte complex formation or dissociation via stimuli‐responsive poly(vinylamine‐co‐N‐vinylisobutylamide)

Poly(vinylamine‐co‐N‐vinylisobutylamide) or poly(VAm‐co‐NVIBA) was evaluated for its ability to stabilize double‐stranded DNA (dsDNA) with the controlled formation or dissociation of polyion complexes. The poly(VAm‐co‐NVIBA) copolymer consists of the cationic poly(vinylamine) (VAm) that electrostatically binds to the anionic DNA and the thermally responsive poly(N‐isobutylamide) (NVIBA) that helps limit the strength of the electrostatic interaction and prevents the alteration of the DNA helical structure. Agarose gel electrophoresis showed the successful complexation between dsDNA and poly(VAm‐co‐NVIBA). Moreover, DNA was released from the complex at 65 °C, but not at 25 °C. Thus, the NVIBA component in the copolymer played an important role in controlling the process of complex formation or dissociation according to the pH and temperature. The results showed that the molecular design of polycations with a thermoresponsive part is a potential strategy to allow the controllable formation and dissociation of the copolymer/dsDNA complex while avoiding changes to the DNA helical structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43852.     

Effect of hydraulic retention time on hydrogen production and chemical oxygen demand removal from tapioca wastewater using anaerobic mixed cultures in anaerobic baffled reactor (ABR)

This study evaluated hydrogen production and chemical oxygen demand removal (COD removal) from tapioca wastewater using anaerobic mixed cultures in anaerobic baffled reactor (ABR). The ABR was conducted based on the optimum condition obtained from the batch experiment, i.e. 2.25 g/L of FeSO₄ and initial pH of 9.0. The effects of the varying hydraulic retention times (HRT: 24, 18, 12, 6 and 3 h) on hydrogen production and COD removal in a continuous ABR were operated at room temperature (32.3 ± 1.5 °C). Hydrogen production rate (HPR) increased with a reduction in HRT i.e. from 164.45 ± 4.14 mL H₂/L.d (24 h HRT) to 883.19 ± 7.89 mL H₂/L.d (6 h HRT) then decreased to 748.54 ± 13.84 mL H₂/L.d (3 h HRT). COD removal increased with reduction in HRT i.e. from 14.02 ± 0.58% (24 h HRT) to 29.30 ± 0.84% (6 h HRT) then decreased to 21.97 ± 0.94% (3 h HRT). HRT of 6 h was the optimum condition for ABR operation as indicated.     

Mathematical modeling of heavy metals contamination from MSW landfill site in Khon Kaen, Thailand

Kham Bon landfill site is one of many municipality waste disposal sites in Thailand which are in an unsanitary condition. The site has been receiving municipality wastes without separating hazardous waste since 1968. Heavy metals including, Pb, Cr and Cd are found in soil and groundwater around the site, posing a health risk to people living nearby. In this research, contamination transport modelling of Pb, Cr and Cd was simulated using MODFLOW for two periods, at the present (2010) and 20 years prediction (2030). Model results showed that heavy metals, especially Pb and Cr migrated toward the north-eastern and south-eastern direction. The 20 years prediction showed that, heavy metals tend to move from the top soil to the deeper aquifer. The migration would not exceed 500 m radius from the landfill centre in the next 20 years, which is considered to be a slow process. From the simulation model, it is recommended that a mitigation measure should be performed to reduce the risk from landfill contamination. Hazardous waste should be separated for proper management. Groundwater contamination in the aquifer should be closely monitored. Consumption of groundwater in a 500 m radius must be avoided. In addition, rehabilitation of the landfill site should be undertaken to prevent further mobilization of pollutants.     

Degradation and detoxification of formaline wastewater by advanced oxidation processes

In this study, advanced oxidation processes (AOPs) utilizing the combinations of UV/H(2)O(2), Fenton, photo-Fenton and the combination of Fenton/photo-Fenton reactions were investigated in lab-scale experiments for the degradation of formaline wastewater. The studied toxic chemicals were formaldehyde and methanol in mixture solution, so-called formalin, which is the embalming agent in mortuaries. The experimental results showed that the photo-Fenton process was the most effective treatment process among the studied AOPs. Pseudo-first-order degradation rate constants of formaldehyde and methanol were obtained from batch experimental data. In the combination of Fenton/photo-Fenton reactions, the results show that applying UV light at an early stage of the reaction might not be necessary for a speedy oxidation reaction of the Fenton process. With Fenton and photo-Fenton processes, mineralization of formaline wastewater can be achieved, as no residual TOC is detected in the effluent after the reaction period. It is suggested that Fenton and photo-Fenton processes are viable techniques for the formaline wastewater treatment as they were able to provide high degradation of formaldehyde and methanol with relatively low toxicity of the by-products in the effluent.     

Effects of iron type in Fenton reaction on mineralization and biodegradability enhancement of hazardous organic compounds

The mineralization and biodegradability increase and their combination of two traditional and two relatively new organic contaminants by Fenton reagents with three different types of iron, Fe(2+), Fe(3+), and Fe(0) were investigated. The traditional contaminants examined were trichloroethene (TCE) and 2,4-dichlorophenol (2,4-DCP) while 1,4-dioxane (1,4-D) and 1,2,3-trichloropropane (TCP) were studied for the relatively new contaminants. The mineralization and biodegradability were represented by dissolved organic carbon (DOC) reduction and the ratio of biodegradable dissolved organic carbon and DOC, respectively. For all four contaminants, Fenton reagent using Fe(2+) was more effective in the DOC reduction than Fenton reagents using Fe(3+) and Fe(0) in most cases. The types of Fe that provided maximum biodegradability increase were not the same for all four compounds, Fe(3+) for TCE, Fe(0) for 2,4-DCP, Fe(2+) for 1,4-D, and Fe(3+) for TCP. When the combination of DOC elimination and biodegradability increase (least refractory fraction) was considered, Fe(2+) was the best choice except for 2,4-DCP which was susceptible to Fe(0) catalyzed Fenton reagent the most. The least refractory fractions remaining after 120 min of reaction were 20-25% for TCE, 2,4-DCP, and TCP and 30-40% for 1,4-D. The iron type in Fenton reaction also affected the type of mineralization kinetics of TCE, 2,4-DCP, and TCP as well as the types of degradation by-products of these contaminants. Some of the by-products found, such as isopropanol and propionic aldehyde, which were produced from Fe(0) catalyzed Fenton degradation of TCP, have not been previously reported.